In many airline accidents, or other aircraft accidents, the only systems that survive in a usable form are the crash survivable memory units (CSMUs) of the flight data recorders (FDRs), cockpit voice recorders (CVRs) and sometimes a flight video recorder. The flight data recorder is a flight recorder used to record specific aircraft performance parameters, such as air speed, altitude, vertical acceleration, time, magnetic heading, control-column position, rudder-pedal position, control-wheel position, horizontal stabilizer, and fuel flow. The cockpit voice recorder records cockpit voices, and possibly other sounds throughout the aircraft, such as conversations between the pilot, ground control, copilot and other flight crew. The FDR, CVR and flight video recorder are generically known as flight recorders. The FDR and CVR can be separate units, although some versions combine both in one unit.
Popularly known as the black box used for aircraft mishap or accident analysis, these units are also used to study air safety issues, material degradation, unsafe flying procedures, and jet engine performance. These International Civil Aviation Organization (ICAO) regulated black box devices are often used as an aid in investigating aircraft mishaps, and its recovery is typically second only in importance to the recovery of any surviving passengers/crew, and victims' bodies. The outer housing of the device can be painted bright orange and is generally located in the tail section of the aircraft, as this location allows the forward section of the aircraft to be a crush zone providing some crush protection for the flight records in the event of a typical crash or collision.
In the event of a crash, the rest of the flight recorders' chassis and inner components are typically mangled, as are other aircraft components. The CSMU is a large cylinder that bolts onto the flat portion of the recorder. The CSMU device is engineered to withstand extreme heat, violent crashes, and intense pressure. In older magnetic-tape recorders, the CSMU can be inside a rectangular box.
The flight recorders are placed in an aircraft, at least in part, for the purpose of facilitating the investigation of an aircraft accident or incident. Consequently, flight recorders can be specified to be capable of surviving the conditions likely to be encountered in a severe aircraft accident. The flight recorder can be specified to withstand an impact of 3600 g and temperatures of over 1000° C., as required by EUROCAE ED-112.
The CSMU of known flight recorders can use three layers of materials to insulate and protect the stack of memory boards that store the digitized flight, voice, and video information. The materials that provide a barrier protection for the memory boards, starting at the innermost barrier and working outward are: a) an aluminum housing which can be a thin layer of aluminum around the stack of memory cards; b) high-temperature insulation which can be dry-silica material approximately 1 inch (2.54 cm) thick and which provides high-temperature thermal protection during post-accident fires, and c) a stainless-steel shell that is about 0.18-0.25 inches (0.64 cm) thick. Titanium can be used to create the outer armor.
In addition to the above requirements/methods which are generally applicable to commercial aircraft, standards are being developed for crash survivable memory units which are used in general aviation, and other standards exist and are being developed for military aircraft. These other methods and developing standards require innovation in the area of thermal protection for the CSMU, because the standards may require different tradeoffs and the general aviation market may require a lower cost unit when compared to the commercial aviation or military markets. Further, CSMUs can be required or envisioned in various other transportation systems, such as marine, train, truck, cars, and motorcycles.
Although existing methods do provide some thermal protection to the CSMU, there still exists a need to continually advance and improve the thermal protection characteristics of CSMUs in order to protect the vital flight data, flight voice, and flight video recorded therein.